Changed wxPropertyCategory to use same cell rendering code as regular properties. This allows labels for category columns other than the first. Rendering code was heavily modified to allow 'merging' of cells when needed.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63012 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/propgrid/propgrid.cpp

@@ -1868,6 +1868,10 @@ void FormMain::PopulateWithLibraryConfig ()
     pid = pg->Append( new wxPropertyCategory( wxT("wxWidgets Library Configuration") ) );
     pg->SetPropertyCell( pid, 0, wxPG_LABEL, bmp );
 
+    // Both of following lines would set a label for the second column
+    pg->SetPropertyCell( pid, 1, "Is Enabled" );
+    pid->SetValue("Is Enabled");
+
     ADD_WX_LIB_CONF_GROUP(wxT("Global Settings"))
     ADD_WX_LIB_CONF( wxUSE_GUI )